Note: Descriptions are shown in the official language in which they were submitted.
365
The invention relates to tne production of dehydrated
intact cooked po-tato cells~ i3 e. potato granules Further,
the invention relates to a single-pass~ continuous process
not requiring the addback of the ~lnal product to the starting
5 materials as required in prior art potato granule processes.
There are numerous disclosure~; in the prior art for
processes -to produce by a direct process dehydr&ted potato
pieces capable o~ reconstitution to a mashed potato~
Great Britain Patent No. 542,125 discloses a process
10 wherein mashed potatoes are dried at a temperature o~ 50-60C.
~or two hours to reach a moisture content of 40 to 60~. The
partially dried mash is then compressed and conditioned ~or
6 to 24 hours, a~ter which it is divided by rubbing through
a ~ieve, and the divided pieces are then dried to completion.
15United States Patent No. 2,750~295 discloses a
process in which mashed potatoesare mixed with ethyl alcohol
and 60~ o~ the moisture is removed by distillation. Additional
alcohol is mixed with the partiall~ dried potatoes to remove
- an additional 35~ o~ the water, and a~ter ~iltration, the
20 unicellular granules are dried conventionally. This process
is too costly and leaves an undesirable residual ~lavor
Also there are man~ prior art processes based on ;
the 'l~reeze-squeeze" approach in which mashed potatoes are
~rozen; thawed; and dewatered to produce a ~riable damp ;;
25 powder which can be dried conventionally. However, such
processes are not satis~actory because o~ economic reasons
coupled with unacceptably large losses o~ solids and
nutrients and resulting sandy texture.
Great Britain Patent No. 740~711 to Templeton
30 discloses a non-addback process ~or making dehydrated potato
; ,
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;5
powder except that addback ls initially used during start-up7
Templeton adds coo~ed potatoes having up to 60~ moisture to
the inlet end of a three trough mixer-evaporator, Each
trough is surrounded by a steam ~acket to keep the product
5 at about 50~C. maximum. Counter-current alr is blown over
the product to evaporate the water as the product progresses
through the mixer. At the outlet end a moist powder is
discharged having below 30~ moisture which is then ~inal
dried, The process is either a batch process or can be run
-10 continuously by adjusting the rate o~ input with the rate o~ ;~
output so that a certain level is maintained in the mixer.
There is no disclosure of the use o~ monoglycerides nor is
there a disclosure that the powder is granulated without
excessive dam~ge during mixing and entrained by the air Plow.
U. S, Patent No. 3,133,797 to Pierson discloses a
; non-addback process ~or dehydrating potatoes in which the
cooked potatoes are mechanicall~ ~orced by a roller through
screen openings separating the mash into aggregates and
are then blown of~ o~ the screen by an air blast. The
20 particles ~all through a d~hy~ r counter-current to a warm i;
air ~low and are then ~inish dried. The end product i8 a ;
mixture o~ granules and powder. A similar process is dis-
closed in U. $, Patent No. 3~517,716 to Carlsen which includes
additional baf~le means and counter-current air flow means
25 to retard the free ~all o~ the comminuted particles through
~ '" ,
the dryer and permit adequate drying thereo~, Neither o~
. . .
these processes disclose the use o~ monoglycerides nor the
granulation o~ the moist mash by passing it through the
dryer and entraining the granulated particles in the air flow
, .
30 to r~move them from the system,
''':;
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.. .... . . .. . . .
U~S. Patent No. 3,009,817 to Hendel discloses a non-
addback process for making dehydrated potato granules. Raw
potatoes are washed, peeled, trimmed, cut and dipped in soaium
bisulphite solution and cooked, The cooked potatoes are mashed,
blended with optional additives which include edible dispersing
agents such as monoglycerly esters of long chamn fatty acids
to increase the ability to absorb water and to reduce stickiness,
and then conditioned by cooling for several hours either at room
temperature or for shorter periods at down to sub-freezing
temperatures. The conditioned, cooked potatoes are then
granulated by subdividing the mash into single cells without
; rupturing the cells by gently mixing in a granulator while
subjecting the mix to a hot air stream to reduae moisture.
Thereafter, the temperature and velocity of the air is increased
and the granulated particles are entrained by the air stream
and carried into a collector and then finally dried. The process
; - is long, requiring asaa minimum 2 to 3 hours from the time the
conditioning step begins. Hendel teaches the elimination of or
shortening the duration of his conditioning step but only in a
` 20 process where portions of the final product are added back to the
! starting materials and even then a cooling step is required. See
also, U.S. Patent 3,009,816 to Hendel for a generally similar
.
disclosure but teaching the addition of a 1-4 hour soaking step
prior to coo~ing in order to increase the water absorption
~; characteristics of the dehydrated granules.
Applicants have found, through the proper use of
monoglycerides to coat the individual intact cooked potato
; cells, a unique process by which ~endel's conditioning step
can be eliminated without the need to use either a cooling
.:
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step or the step of adding back final product to the
startlng materials and applicants achieve impro~ed water
absorption characteristics over prior art granules wlthout
a soaking step. Applicants' process iB quick and
5 effective and a distinct improvement over Hendel's teachings. -
~ .
Cooked potato cells are extremelg fraglle and if
- ruptured during processing, the end products are too rubbery
or stick~ to be utilized in making mealy mashed potatoes. 2~ '
This accounts for the failure of prior art single-pass
10 potato granules processes to make a product of acceptable
quality. In contrast, the product of this invention has a
, ~ .;.. ..
~ more natural, freshly cooked potato flavor. The product is ` ~ ~
.. ~
not sub~ected to repeated handllng and heating and does not
require the protectlve additives necessary in some prior
15 art processe~. The texture is mealy when reconstituted in
contrast to stickiness or a sandy quality characteristic
of prior art products~ In addition, the product of the
invention has improved cold water absorption qualities and
is especially desirable in ~ormulation of fabricated potato
20 snack products such as those described in United States
Patents 3,539,356 and 3,576,647.
The invention includes a process for making a
dehydrated potato product having unique characterlstics
in which raw potatoes are ~irst prepared for cooking in
25 the usual manner by washing, peeling, trimming and cutting.
Optionally, the cut potatoes are dipped in a sodium
bisulphite solution to prevent discoloration and are then
-
; cooked co~ventionally. The cooked potatoes are mixed with
a starch complexing emulsifier in order to separate the
30 cooked potato cells and uniformly coat the separ&ted ce~ls
',
; 5-
. ~ :
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;` . . .... . . ... . .
~ 4~36S
with a ~ilm of the emulsi~ier. This separating and coat-
lng action reduces the cohesiveness o~ the freshly mashed
potatoas and lubricates the sur~ace o~ the cells to
prevent rupture during subsequent processing. The potato-
5 emulsi~ier mixture is then granulated in a mixer-dryer
by mixing the mixture to expose new moist sur~aces f~or
drying without rupture o~' the cells while drying the
surfaces by injecting high velocity hot air directly onto
the surfaces. When the moisture content of the mixture is
10 appro~imately 25-30~ by weight~ intact potato cells and
small agglomerates thereo~ are automatlcally separated from
the mixture and alrli~ted out of the mixer-dryer where they
are separated ~rom the air stream and then conventionally
~; dried to about 8a/Omolsture content", These granules are of a
; .
15 particle size that will substantially pass a 4rO mesh
'~ screen?havé high cold water absorption characteristlcs and
produce a mealy mashed potato when rehydrated in water.
It is an ob~act of this invention to produce de-
~,~ hydrated potato granules without the use o~ addback and
20 without the necessity ~or conditioning the starting
j~ materials. It is an ob~ect o~ this invention to use whole
'~r potatoes without the necessity o~ precooking and cooling.
It is an ob~ect o~ this invention to use a process
which can produce granules suitable ~or ~inal drying within
25 45 minutes a~ter the mashed potatoes a,re ready ~or granu-
lation and drying.
It is an ob~ect o~ ~is inventlon to provide a ;
,t~,',',.,~ product that is 1QW in additives and has unusually high
cold water absorption characteristics.
Other ob~ects will be clear from the description
. :
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and claims that follow. ,~
The present invention in one aspect, resides in a
direct process for the production of dehyd~a~ed;potato produ~t
comprising the steps of: (a) preparing potatoes for cooking; i:
~b~ cooking the prepared potatoes; (c) mixing uniformly with
the cooked potatoes a starch complexing emulsifier in the ',' ' .
concentration of about 0~30-2.0% by weight of the total solid .,~
matter, said emulsifie~ added to said mixed cooked potatoes in .' ~:
a form such that it is dispersed throughout said mixed cooked , ~',
.
. 10 potatoes whereby it complexes the soluble amylose starch frac-
~.~ . ..
tion of said cooked potatoes ther~by reducing the cohesiveness
of said potatoes, and lubricates and coats the surface of the
cells of the cooked potatoes with the emulsifier such that they ',
are not ruptured during the subsequent granulating step, and
directly (d) granulating khe mixture of step (c) by ~1) mixing
the mixture using sufficient mixing action to expose continually , ,
new surfaces for drying without rupturing the coated cells and
by (2) reducing the moisture of the mixture to about 25-30% ,'
by injecting heated air on the surfaces of the mixture so that ,~
intact potato cells and agglomerates of intact cells are , ',
separated from the mixture; performing steps (c) and (d) before o, ?
an~ significant conditioning of a,aid mixture can take place
whereby the conversion of amylose to its insoluble retrograded ,"
.... .
'' form is prevented; ~e) airlifting the granulated cells and
agglomerates by entrainment in the hea~ed air; (f) separating
the airlifted materials from the heated air; and (g) drying .
'.~ the separated materials to a final moisture content of about
.. 7-8% by weight.
,~ In a further aspect this invention resides in a ;
granular dehydrated instant mashed potato product with unaltered
'' natural flavor consisting essentially of single intact cooked ..
:`:
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36~
potato cells and small agglomerates t~ereof coated wlth starch
complexing emulsifier and containing amylose in unretrograded
soluble form and suitable for rapid reconstitution in hot or
cold water to form a mealy mashed potato, said product being
characterized by being reconstitutable to a non-pourable mix
when rehydrated with about 4.85 parts by weight of cold water
per 1 part of said product.
In another aspect the invention resides in a direct
process for the production of dehydrated intact cooked potato
cells and small agglomerates thereof comprising the steps of: :
~a) preparing potatoes by washing and trimming; (b) cooking the
prepared potatoes to completion; (c) admixing a starch complexing
emulsifier uniformly with said cooked potatoes at a temperature
above the melting point of said emulsifier and in a concentration
so that said.emulsiier comprises about 1.0~ of the total solid
matter present, said emulsifier dispersed throughout said mixed
cooked potatoes whereby it complexes the soluble amylose starch
fraction of said cooked potatoes thereby reducing the cohesive-
ness of said potatoes, and thereby lubricating and coating the
cells of said cooked potato with said emulsifier such that they
are not ruptured during the subsequent steps (d) - (f); (d)
:
mixing said coated potato cells in a mixer-dryer using
::
, sufficient mixing action to expose continuously new large drying
: surface areas without rupturing the cells while simultaneously
.. ~e~ injecting high velocity heated air onto the surface areas of -
the mixture to lower the moisture content of the coated cells;
(f) granulating the coated cells when the moisture content has :
;~ been reduced to the range of about 25-30%, thereby separating
. single cells and agglomerates; performing steps (c), (d), (e) ~.
and (f~ before any significant conditioning of said mixt~re can
take place; (g) entraining peel particles along with the separ-
ated single cells and agglomerates from.the mixer-~ryer in
. :......... ,
~ 7
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, ,.. -: .: , . . . . - . :
i365
heated air;
~h~ reducing the velocity of the air ~arrying entrained
; material to a point at which the larger of the entrained agglo-
merates above the size that will pass a 40 mesh screen fall from
entrainment back into the mixer-dryer while the peel particles
along ~ith the single cells and the smaller o~ the entrained
agglomerates remain entrained and are removed from the system; ~`
(i) separating the solid matter from the entraining air; `~
(j) drying the solid matter to a moisture content of about 7-8~;
and (k) separating the peel particles from the dried solid matter,
~hereby isolating the dried intact cells and small agglomerates.
In the drawings which are annexed hereto and illustrate
by way of example particular aspects of the present invention:
Fig. 1 is a cross sectional view o the mixer-dryer
taken along the lines 1-1 of Fig. 3.
Fig. 2 is a cross sectional plan view of the mixer-
dryer showing air distribution means and mixing paddle structure
taken along the line 2-2 of Fig. 1.
- Fig. 3 is a cross section end view of the mixer-dryer
taken along the line 3-3 of Fig. 1 and showing the expansion
hood and mixer paddles.
The production of potato granules requires preparing
and cooking potatoes, separating intact potato cells without ;~
rupturing them and then drying the separated cells. Ruptured
cells liberate free starch which makes the resulting dried
product unacceptable in that when it is rehydrated with water
to form mashed potatoes, the potatoes are sticky or gummy.
In this description, the term "agglomerate" is applied
s to a group of intact po$ato cells which have been separated
but which adhere in loose random fashion. In contrast, the
term "aggregate" is applied to particles of potato comprising ~ ~`
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intact cells which ha~e not been previously separated, such
as would be formed by forcing cooked potato through a screen
aperture followed by drying. The particles would be dense
and would rehydrate poorly,
The first stage of processing is to prepare the
potatoes. Raw potatoes are lye peeled, washed and trimmed as
usual, The potatoes are then dipped into a sodium bisulfite
solution (1/2% as S02) to neutralize any residual lye prior to
cooking, This results in a S02 content in the finished product
which is far below the amount normally found
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in dehydrated instant mashed potato products
The process o~ this invention ls a low additive
process. It is not necessary to add large amounts o~
additives, such as S02-containing salts, chelating agents, `- ~;
antioxidants and the like~ to prokect the product during
the process. Normally, commercial potato granules contain
200-500 ppm S02 in addition to antioxidants and other pre-
servatives which are necessary to prei~ent oxidation and
discoloration during repeated and lengthy heating~ standing~ -
and drying periods. All o~ these additives are eliminated
in the present process. ~ndeed but for the trace of S02
and the starch complexing emulsi~ier, described below,
there are no other additlves necessary to the process.
,;, . .
; Although the pre~erre~ embodiment uses completely prepared
15 potatoes, we have operated the process success~ully, with
minor alterations~ on unpeeled potatoes. Large peel
pieces are quickly entrained in the mixer-dryer described
below and can be separated subsequently ~rom the intact
. ;............ . .
cells by screenlng. ;
.... .
` 20 The next stage of processing is cooking the pre-
pared potatoes. It will be obvious to one skilled in the
art that an~ method o~ cooking potatces to completion can
be employed in the inventive process. Although we pre~er
.
to cook with atmospheric steam, hot oil or hot water
25 cooking are likewise satis~actory.
, ~ .
The next stage of processing is separating the
cooked potato cells and uniformly coating the separated cell ;~
; sur~aces with a ~ilm o~ starch complexing emulsifier. This
; :,
step is pre~erably accomplished by partially mashing the
30 cooked potatoes as by ricing and immediately mixing with a
8.
,' ,~ ;.
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~4~3~S : -
starch complexing emulsifier, such as glyceryl monostearate at
a temperature above its melting point. During the mixing,
which is necessary to accomplish complete cell separation, the
emulsifier is uniformly distributed and the surfaces of the
separated cells are uniformly coated with a thin film of the
melted emulsifier. This coating accomplishes two functions. As
is known in the prior art, starch complexing emulsifiers complex
with the soluble amylose starch fraction that is at least
partially responsible for the cohesiveness of freshly mashed
potatoes. Such emulsifiers also appear to lubricate the potato
cell surfaces so that they are not ruptured during subsequent
moderate mixing and drying.
As one example we have successfully mixed the potatoes
at a temperature of about 190F using a distilled glyceryl
monostearate at a concentration of 1~0% by wei~ht ba~ed upon
potato solids, to coat the intact potato cells with a film of
monoglyceride.
; The coating action can also be accomplished by adding
the emulsifier in dispersed form, but this technique introduces
into the system appreciable additional water which must be
:; :
removed in the drying step. However, the advantage of this ;
alternative is that the coating action takes place below the
melting point of the emulsifier, An example of a suitable
dispersed emulsifier is one made by mixing 1.1 parts of weight
of glyceryl monostearate with 25 parts of water at 160~F. to `
form a stable creamy colloid.
~ lthough we prefer to use monoglyceridès sùch~Sas
glyceryl monostearate as the starch complexing emulsifier, test
runs were successfully conducted using other starch complexing
,
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, . .. . . . .
3~;S ~;~
emulsifiers. Sodium stearyl fumarate, calcium stearoyl *~
lactylate, sodium stearoyl-2-lactylate, and propylene glycol
monoesters were all effective in the same concentration as used
for the monoglycerides -- 0.3-2.0~. Commercial propylene glycol
monoester contains about 11% monoglycerides.
The concentration of the starch complexing emulsifier
was found to be very importa~t. When the process was conducted
using the emulsifier at a concentration below 0.3~ by weight
based on total solid matter, the mash became progressively more
rubbery during subsequent mixing and eventually formed an
unmanageable ball with no trace of granulation. At the other
extreme, there was no advantage in adding more than ~% on a
solids basis, It appears that adequate "lubrication" and
complexing of the soluble amylose are accomplished in the
range of .3 - 2~.
The temperature of the mashed potato-emulsifier mix
was likewise found to be very important. When the potatoes
are allowed to cool before the addition of the emulsifier
resulting in a mix temperature below the melting point of the
emulsifier, the separated intact potato cells are not adequately ;
coated or lubricated and the soluble amylose is nok complexed.
As a result, the mix contains unmelted emulsifier particles and
does not granulate properly, and a product comparable in particle
,j , : .. .
size to potato granules cah~t be-produced. G~yceryl
monostearate, the monoglyceride used in the preferred embodiment,
has a melting point of 65-70C. (149.0 -- 158.0F.) When the -
^' temperature of the mix is maintained above this value, uniform ;
.
;~ distribution of the monoglyceride can be accomplished without
damage. We prefer to mix at a temperature of at least 160F. ~- -
3Q to assure complete coating of the potato cells. Monoylycerides
of o~her comparable fatty acids, such as of lauric and-palmitic
;,: , :
" 10 '~ '
.. ; .
'
~4~65
acids, have lower melting points and could undoubtPdly be
distributed at temperatures below 150F. but abo~e~their
melting points. It is essential that the monoglycerides or
, .
other starch complexing emulsifier employed, be uniformly
distributed. The mixing steps ou~lined above accomplished
this, although any other non-damaging means of distribution
would be equally sati~factory. -
In an alternative embodiment, the cooked potatoes
are slurried and defective portions, such as peel and eye
fragments, are removed by screening to produce a defect-free
slurry of intact potato cells consisting of about 18% potato
solids. The slurry is then intimately mixed hot with mono-
glycserides and may be added to the mixer-dryer ~desaribed below)
as the sole source of potato solids. The dry end product is
substantially defect-free. Of course, the extra water added
to form the slurry has to be additionally removed during drying
, .,, ~.
~ of the product. `;
f~ . The ~ext stage of processing is granulating the cooked ;~
potatoes by mixing and drying them in the mixer-dryer and then
airlifting the granulated particles out of the system for final
treatment.
One apparatus for performing these steps is shown in
, Figs. 1, 2 and 3 and will be first described. It ls understood
~5 that additional apparatus may be ~mployed to perform these
same steps.
~` Referring to Fig. 1, the inlet end of the mixer-
.
dryer is shown generally at 12. Inside the mixer-dryer -
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are located two parallel shafts 8 which rotate (drive means
not shown) in the same direction and carry intermeshing
paddles 9 with a cross-of-Lorraine con~iguration. As shown
in Fig. 2, hot air enters the air distribution header 1 and
~ 5 is controllably mixed with cold air through dampers 2;-~ and
; is then led through outlets 3 and tubes 4 where it is sent
at high velocity directly into the troughs 5 o~ the mixer-
dryer. As best shown in Fig. 3, a hood I0 with 20 diverging
sides 11 sits atop the mixer-dryer. The angled sides 11
10 function to prevent product buildup thereon and also ~unction
as a di~fuser to reduce air velocity as air progresses
toward the top 6 of the hood and out the exhaust duct 7~
In the operation o~ the mixer-dryer, it ~as been
~ound that i~ high velocity heated air is directed onto the
15 mashed potato - emulsi~ier mixture, the moisture content which
was initially about 80~ can be lowered without the rupture
of cells or the formation o~ a hard, horny crust known as
case hardening. The mixing constantly exposes new drying sur-
faces to the heated air. `~
~ The mashed potato-emulsi~ier mixture is continuously
~ed into the mixer-dryer at the inlet end 12 at the rate o~
about 24 pounds per minute. At this location the mixture
resembles a dough and has a moisture content initially at
about 80~. As the mix progresses (rightward in Fig. 1~ in ;~
25 the mixer~dryer, the dough begins to separate into small
particles when the moisture content has been reduced to about
% under the drying action of the high velocity hot airO
Farther rightward in the mixer-dryer where the moisture `
` content is reduced to about 25-30~, the mix begins to
30 granulate to particles which are then entrained in the air
.
::
12.
`` ~ .
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~04~3~5
flow. The air velocity is ad~usted so that single intact
cells or small agglomerates of' about 40 mesh consistin~
of several intact cells are alr llfted and carried out of
the system along with smaller quantitie3 o~ larger ~ractiorls,
;5 such as na-tural ~ibers and small pieces of residual peel.
This granulation is sudden and unexpected and does not start
until the moisture level is near 25-30C~. Mos-t of the
entrained agglomerates larger than about 40 mesh remain in
the system by ~alling back into the trough 5 and are ~urther
10 granulated and dried. This separation o~ larger particles
is accomplished by expanding the area of hood 10 above the
mixer~dryer to reduce the air velocity rapidly, (see Fig. 3)
Single cells and small ag~lomerates remain entra~ned and
are removed ln the exhaust air through exhaust duct 7 ~or
-15 subsequent collection and final drying.
The process is made continuous by adding potato
solids in the ~orm o~ mashed potato-emulsi~ier mixture at the
inlet end 12 o~ the mixer roughly equivalent in weight to the
- potato solids which are separated ~rom the system. ;-
The optimum speed of the mixing means would
undoubtedly be di~erent ~or each di~ferent piece o~ mixing
equipment, A rotational speed must be chosen which will be
slow enough not to throw the potato mix out o~ contact with
the mixing means and not to rupture the tender potato cells
, 25 by impact or abrasion and yet will be ~ast enough to expose
, continuously enough new moist sur~aces to allow rapid drying.
We pre~er the mixer shown in Figs. 1-3 which is used in
commercial potato granule operations to blend cooked potatoes
and addback uni~ormly to a damp powder. On this mixing
30 equipment a rotational speed o~ 100-120 rpm is optimum and ~ -`
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iO41365 . ?
was found to be e~ficient and non-damagln~. 60 rpm does
.~ not expose suf~icient new drying surfaces and 160 rpm~throws
the product excessively.
rrhe location, temperature and velocity o~
. 5 in~ection of the hot air is important to satis~actory
- results and drying e~ficiency.
. ,: .
As is evident ~rom Figs. 1 and 2, we in~ect hot
. air dow~ward through the multiple tubes 4 along the entire - ~
length o~ the mixer-dryer, although other methods of air ~ `
10 addition will be obvious to one skilled in the art
~ It is desirable to use temperatures as high as
; possible without resulting in scorched material. We have
~ound temperatures o~ 500~ to be damagin~ but no damage
resulted when air was applied at 470F. It will be
15 obvious that the use o~ higher temperature~ would reduce .
; the required residence time in the mixer and would reduce ~. ~
. any possible physical damage due to the action o~ the mixer . ~.
s;¦ itsal~ We have also ~ound that higher air temperatures can :
be applied at the inlet end where moistures are abo~e 50~
20 than can be applied at the exhaust end where moistures are
about 30~. For example, we have ~ound that temperatures at :~
the outlets o~ tubes 4 o~ 420F. at the inlet end, 400 in
~ the center section and 350F. at the downstream end are satis~
,,,,.,,.1 ~actory.
Air velocities must be selected within a range in
which single cells and small agglomerates are removed from
~ the system by entrainment but larger agglomerates are
.:. continually contacted by the mixing means until granulation
~` is essentially complete. In our equipment, velocities above
~ 30 9000 feet per minute at point o~ in~ection had the same
i . ' ~'
.~; 14.
~ .
~,....
, . . .
~0~
; detrim~ntal effect as excessive mixer speed -- the product was
suspended and did not mix properly. At the other extreme,
velocities below 4000 feet per minute at point of injection
resulted in unsatisfactory drying. We have found an air velocity
of 6400 fpm in the tubes 4 to be satisfactory. This resulted in
an upward air velocity of about 400 fpm at the top of the mixer
dryer 5 and of about 160 fpm at the top of mixer hood 6.
Certain precautions must be taken in the handling of
the cells and agglomerates which are entrained. If all material
entrained from the mixing area is removed from the system, the
end product is too moist, too coarse in particle size, and does
not rehydrate quickly and completely after drying. As mentioned
above, in the expanding area of hood 10, air velocities at the
widest point reduce to about 160 fpm. This assures that large
dense agglomerates - su~stantially larger than 40 mesh -- will
drop back into the mixer to undergo further granulation and not ~
be removed from the system. Since the exhaust duct 7 is located -~-
toward the inlet end 12, this allows the large agglomerates which
are dropped from entrainment in the expanded hood to be deposited
into the mix nearer the inlet end where moistures a~e higher.
Thus, after arriving at equilibrium conditions, the product
at the inlet end of the mixer-dryer is about 65% - 75% in
moisture; the product in the center is about 35~45% in moisture;
.~ .
and the product in the opposite end has a moisture content of ~
.. .
about 25-30%o The product temperature throughout the mixer-
dryer is about 115-120 F. The rotational speed of paddle shafts
..
8 was about 100 rpm, and the level of product at rest in the
; mixeF-dryer stabiliZed at a point
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about rnidway between sha~ts ~
1`he mixing means utilized in the mixer-dryer gave
satis~actory results. Other mixing devices would likewise
be e~pected to give comparable results i~ the mixing action
during the time the product is exposed to mixing is not
damaging to the tender intact potato cells and yet the
action is sufficient to constantl~ expose new high moisture
sur~aces and to break up agglomerates too large to be
~ removed by entralnment in the heated airO For example,
- 10 initial drying can be further accelerated by substituting
closely set pin paddles in the first third of the mixer-
dryer where moistures are high.
; The time necessary to convert the hot mashed potato- `
emulsi~ier mix to a ~inc granulate ready ~or ~inal drying is
approximately 30-45 minutes, This is only a ~raction o~
the time required in prior art potato granule processes `~ ~
The brevity of the process inherently results not only in ~ -
improved quality but in novel physical characteristics
Due to the rapid completion of drying, natural ~lavor is
retained and the soluble am~lose fraction o~ the starch is
not appreciably retrograded to its insoluble ~orm prior to
.
; drying By retention o~ amylose in its soluble ~orm, the
product of the lnvention rapidly absorbs appreciably more
i` cold water than commercial potato granu]es. In contrast,
commercial potato granule processes require length~ holding
periods prior to drying ~or the purpose o~ accomplishing
retrogradation or insolubilization o~ amylose since this
toughens potato cells and aids in their separation in intact
~orm. Such a retrograded product, although capable o~
~orming excellent mashed potatoes when reconstituted in very
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hot water, does not absorb cold water appreciably7thereby
limiting its appllcations.
The ~inal stage o~ processing is ~inal drying and
dehydratlng the granulated particles The intact cells
and small agglomerates entrained in the exhaust air duct 7
have a moisture content o~ about 16-2~o and are separated
by conventional means, such as, b~ a low velocity cyclone
- collector ~not shown) which does not sub~ect the particles
to forces which would result in cell breakage during
collection. At the collector discharge, the moisture
content is about 12-18~, and the product is easil~ dried
~i to the desired ~inal moisture content o~ about 7-80,~ by
conventional mean~, 5uch as a hot air ~luid bed dr~er,
The dried product had a particle size substantially
passing a standard 40 mesh screen and about 70~ by weight
; passing through a standard 60 mesh screen. The small plus
40 mesh fractlon comprises ~ibers and other undesirable
particles and is discarded. The dried product is made into
mashed potatoes ~y rehydrating in 5 parts by weight o~
salted water-milk mixture heated to boiling The texture
and appearance are excellent and the product is judged to
.,.~ .... .
have a more natural potato ~lavor than other commercial
instant mashed potato products This is attributed to
,. .,~ .
such ~actors as lack o~ additives, short processing time
and low product temperature during processing.
Although exact parameters have been determined ~or
our specially designed equipment, it will be obvlous that
adjustments would undoubtedly be required ~or other
equipment designs.
Another embodiment of the lnvention u~ilizes a
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predrying step which is optional. The uniform hot mashed
potato-monoglyceride mix with completely coated potato
cells is riced onto a perforated screen drying sur~ace and
predried until about 75~ o~ the moisture is removed by
5 passing air heated to about 140-150F. over the mix for
about five minutes. The predried mash is then ~ed into the
mixer-dryer operated in the manner previously described. `
The predried mash granulates in about 4 minutes. The
~inal product is good in quali~y ~ut contains a higher
10 percentage of larger agglomerates. When the predrying step
is used to remove up to 56-68~ of the moisture ln the mash,
the predried mash granulates in 6-12 minutes. The dry
~inished product is excellent in quality and comparable in
granulation to the product produced by utilizing the pre-
15 ~erred embodiment,
1.1
In recent years, processes ~or making instant mashed
., .
potato products, such as potato granules and potato flakes,
have incorporated precooking and cooling steps prior to
cooking. This sequence of steps results in a tougher cell -
25 that resists rupture during processing and makes a more
mealy ~inished mash However, these steps require
additional equipment and greater water usage and result in
appreciable solids loss. We have operated our inventive
process both ways and have ~ound no advantages( to either.
25 Thus, our process, by eliminating the necessity o~ the
^`~ precook-cool steps prior to cooking, is simplified and
gives increased yields with less water usage.
- Additional research has shown that the cold waterabsorption and other physical characteristics o~ the de-
.. .
30 hydrated granules o~ this invention can be var:Led by ~-
. . .
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adjustment of feed rates and air temperatures. Of course,
higher feed rates require hotter air to accomplish equivalent
drying in a given piece of e~uipment. As feed rate increases,
`~ the residence time within the mixer~dryer decreases and the
cold water absorption of the resulting end product increases.
When the feed rate is decreased, the time :in the undried state ;
is increased, apparently allowing retrogradation of soluble
amylose to take place, resulting in an end product with reduced
cold water absorption--closer to that of conventional potato
granules. T~erefore, within limits, the inventive process allows
one to produce end products having different physical character-s
istics wh~ch cannot be duplicated by potato granules produced
by prior art proces~es and which give the product of the
invention utility in specialized applications in which potato
granules are not satisfactory.
In arriving at the preferred embodiment, objective
tests were developed or utillzed to advantage. For example, an
estimation of cell rupture can be obtained by a variation of the
Blue Value Test in which free starch is reacted with iddine and
the depth of the blue color is measured objectively by light
; transmission. By varying only the percentage of monoglycerides,
.,. ~
for example, and testing the product periodically for cell
rupture during mixing, it was determin~d that mixes containing
0.75% glyceryl monostearate or higher by weight of solids showed
no evidence of cell rupture (decrease of light transmission)
even after 25 minutes of mixing. In contrast, mixes with 0.50% -
monostearate showed no rupture after 15 minutes, but some
rupture resulted from prolonged mixing. When cooked mashed
,~ " ~ . .
; potatoes with no monoglyceride were used, appreciable rupt~re
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was detectable in less than 5 minutes and shortly thereafter an .. ; .
unmanageable mass resulted. .
In a further aspect of our studies, an attempt was
made to substitute oil for monoglyceride on the theory that
lubrication alone might prevent cell rupture during the mixing~
: . . .
drying operation. It was found that the required granulation ~ ~
could not be obtained with oil alone, although oil in the ~: .
concentration of a . 1 to 1.0% of the solids in combination with . :.
monoglycexide promoted granulation. This substantiates the .~: :
.
theory that the starch complexing emulsifier complexes the
soluble amylose in the hot mash, thereby reducing the cohesive-
ness sufficiently 50 that the tender intact potato cells when
coated with additional emulsifier are lubricated sufficiently so
that they do not rupture during the mixing-drying steps.
Although it has been long appreciated that these emulsifiers ;
complex soluble amylose, it has not been known prior to appli~a ;:
cants' invention that these starch complexing emulsifiers could
be incorporatêd into mashed potatoes in a way which would allow
separation and drying of intact cells to produce a new product
with the appearance of conventional potato granules but having
new and useful characteristics completely different from potato
granules of the prior art. ~he greatly sho.rtened processing time
at low product temperatures from starting mashed potatoes to
.,. ~ .
finished dried product (approximately 30-45 minutes) apparently
, obviates the necessity to add preservatives and antioxi~ants
:.. , during processing as is required in commercial prior art instant
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mashed potato processes both to protect the product during
processing and to impart stability during storage. This
is a distinct advance in the art~sinGe such additives are
restricted in many countries and are b~comin~ less
5 acceptable e~erywhere. -~
Comparative analysis o~ applicants' product with
typical commercial potato granules and potato flakes are
shown in the ~ollowing table:
Commercial Commercial
Appllcants' PotatoPotato
10 Procedure Product GranulesFlakes
Soluble Starch
; Hot Extraction (1) 50.5 5200 4.o
Cold Extraction (2) 100.0 100.0 56.5
S2 (ppm) o-80.0 380.0 375-5
BHT (antioxidant-ppm)(3)o O ~ o 14 2
15 Recipe Rehydration Ratio(4) 5.5:1 4 8:1 6 0:1
Cold Water Absorption (5) 4.85:1 3.2:1 5.75:1
Amylograph Units
Cold (6) 2300 545 33
Hot (7) 54 650 1~50
20 Flavor Evaluation ~resh Potato Bland~tarchy
Texture Evaluation Verg good Ver~ good $1ightly
Sticky
(1) ~ transmisslon, 185F. extract, 0.1~ solution with iodine
added
(2) ~ transmission, 70F. extract, 0.1~ solution with iodine ~ `
added. -
(3) Butylated hydroxytoluene
25 ~4) Parts o~ boiling liquid per part of product required to
~ make mashed potatoes ~-
i~ (5) Parts o~ water at 70F. absorbed by 1 part by weight product
I (6) 100 parts product, 400 parts water, 10 minutes at o-4c.
(7) 75 parts product, 450 parts water, 45 minutes star-ting
` 30 at 25C. and ending at 92 5C
21.
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The above data show that the product o~ the
invention is comparable to potato granules in soluble starch
and far less than pot~-to ~lakes.
The sul~ur dioxide value of the product is much
5 lower than fl~kes and granules which are comparable. ;
The product is far above potato granules and
slightly below potato flakes in the ability to absorb hot and
cold liquid.
- The product has a cold amylograph viscosity ~ar
., .
10 higher than potato granules and slightly lower than potato -
flakes. The hot amylograph viscosity is higher than potato
flakes and half way between flakes and potato granules.
The product was ~udged to have superior flavor and
texture when compared to potato flakes and a superior ~lavor
15 to conventional pota-to granules.
' Unless otherwise stated herein all percentages
are by weight,
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